add '#define SOFT_SERIAL_PIN D0' to keyboards/qwertyydox/config.h,keyboards/qwertyydox/rev1/config.h

keyboards/qwertyydox/config.h

@@ -49,6 +49,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 /* Set 0 if debouncing isn't needed */
 #define DEBOUNCING_DELAY 5
 
+/* serial.c configuration for split keyboard */
+#define SOFT_SERIAL_PIN D0
+
 /* Mechanical locking support. Use KC_LCAP, KC_LNUM or KC_LSCR instead in keymap */
 #define LOCKING_SUPPORT_ENABLE
 /* Locking resynchronize hack */

keyboards/qwertyydox/rev1/config.h

@@ -49,6 +49,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 /* Set 0 if debouncing isn't needed */
 #define DEBOUNCING_DELAY 5
 
+/* serial.c configuration for split keyboard */
+#define SOFT_SERIAL_PIN D0
+
 /* Mechanical locking support. Use KC_LCAP, KC_LNUM or KC_LSCR instead in keymap */
 #define LOCKING_SUPPORT_ENABLE
 /* Locking resynchronize hack */

quantum/split_common/split-keyboards-list.txt

@@ -12,7 +12,7 @@ ok keyboards/levinson/rules.mk:SPLIT_KEYBOARD = yes
 ok keyboards/miniaxe/rules.mk:SPLIT_KEYBOARD = yes        # Use shared split_common code
 ok keyboards/nyquist/rules.mk:SPLIT_KEYBOARD = yes
 ok keyboards/quefrency/rules.mk:SPLIT_KEYBOARD = yes
-keyboards/qwertyydox/rules.mk:SPLIT_KEYBOARD = yes
+ok keyboards/qwertyydox/rules.mk:SPLIT_KEYBOARD = yes
 keyboards/redox/rules.mk:SPLIT_KEYBOARD = yes
 keyboards/rorschach/rules.mk:SPLIT_KEYBOARD = yes